Pulmonary Arteriovenous Malformation (PAVM) is a
direct communication between branches of the pulmonary arterial and venous
vessels representing right-to-left shunting and therefore not participating
in pulmonary gas exchange. Usually congenital (70% are associated with
Osler-Rendu-Weber Disease), less commonly acquired (hepatic cirrhosis,
mitral stenosis, trauma, actinomycosis, Fanconi Syndrome).
Pulmonary Arteriovenous Fistula; PAVM; Rendu-Osler-Weber Syndrome;
First described in 1896 by Henry Jules Rendu after his description
of telangiectasia and epistaxis. Sir William Osler reported a family known to have
hereditary hemorrhagic telangiectasia in 1897. In 1907, Federick Weber described the other
Unknown, but very rare. Approximately 10% of the
cases are identified during infancy and childhood, with a gradual increase
through the fifth and sixth decades. Only about 20 cases have been described
in neonates. Frequency in United States, 1:39,216 persons. In some regions
of France, 1:2351 persons has been reported.
Unknown. Male predominance during the neonatal
period, but female preponderance (2:1) in adults.
The exact pathogenesis of PAVM still unknown.
Pulmonary lesions function as right-to-left shunts and may cause hypoxemia
or paradoxical embolization. Histologically, there is endothelial and
smooth-muscle cell degeneration, defects in the endothelial junctions, and
weakness of the perivascular connective tissue. Weakness of the vessel walls
may predispose to hemorrhage despite normal coagulation and platelet
functions. Autopsy results show that 75% of patients had unilateral
disease, 35% had multiple lesions, and about half of the latter had
bilateral lesions. The PAVM can be classified as simple (those with a single
feeding segmental artery and a single draining vein) and complex (two or
more feeding arteries or veins). The pulmonary artery pressure is normal or
low in nearly all patients with PAVM.
The diagnosis is usually suspected from the clinical
history. The classical radiological sign on a chest radiograph is that of a
round or oval mass of uniform density, frequently lobulated, but sharply
defined, found most often in the lower lobes. Shunt fraction measurement in
100% oxygen is a sensitive and reasonably specific diagnostic test for
PAVM. The presence of a PAVM can be further evaluated via contrast
echocardiography, radionuclide perfusion lung scan, 3D helical CT scan, or
MRI. However, pulmonary angiography remains the standard criterion in the
diagnosis of PAVM.
Symptoms vary from being totally asymptomatic to
severe with presentation in childhood with cyanosis and shortness of breath
on exertion, congestive heart failure, or respiratory failure. Murmurs or
bruits over the site of the PAVM may be present in half the patients and
louder during inspiration. Increased FiO2 (fraction of inspired oxygen)
may not significantly improve oxygenation. Secondary polycythemia is present
and the degree depends on the severity of cyanosis. The condition is
associated with hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber
syndrome) in 60 to 70% of patients; conversely, 15 to 30% of patients
with hereditary hemorrhagic telangiectasia have PAVM. Hemoptysis from
rupture of the lesions may occur. Thrombosis may occur within ...